Numculator is compact desktop calculator with some interesting and unusual features.

The program runs in the background, for instance, by default popping up when you press the Num Lock key. The interface is just a one-line text box, no buttons to click, so you can start calculating immediately by typing on your numeric keypad.

Everything you enter is recorded in Numculator's history. Reviewing this is as easy as tapping the down arrow, or you can save the entire history as a text file.

Once you've finished your calculations, pressing Ctrl+Enter immediately closes Numculator and pastes the final figure into the previous document. (Of course you can also copy any intermediate figure to the clipboard, as usual.)

Perhaps best of all, just about every aspect of the program is configurable. You can tweak its formatting rules, rounding, alignment, font, transparency, hotkey - there are even 20+ skins to choose from.

Verdict:

Numculator has only limited expression support, but it's configurable, easy to use, and if your math needs are simple then it'll serve you very well.

There's a vast amount to learn, of course, and that's even before you start building your game. But there's plenty of documentation, tutorials, demos and sample projects to point you in the right direction.

The package is now entirely free, too - no annoying limitations, nag screens or anything else. Epic now only requires that you pay a 5% royalty after the first $3,000 of revenue per product per quarter. And even then, you "pay no royalty for film projects, contracting and consulting projects such as architecture, simulation and visualization."